Wireless communication method and wireless communication apparatus

ABSTRACT

A wireless communication method wherein the power consumption can be reduced as compared with the conventional one and a wireless communication apparatus can synchronize its super-frame with the super-frame of another wireless communication apparatus in an ad hoc network. According to this method, in the ad hoc network where a plurality of wireless communication apparatuses use broadband signals to data-communicate with each other, a wireless communication apparatus transmits an end tone ( 201 ) for identifying the end of a super-frame ( 221 ), and when another wireless communication apparatus receives the end tone ( 202 ), it synchronizes the end of its super-frame ( 221 ) with the end of the foregoing super-frame ( 221 ). In this way, the super-frames ( 221 ) can be synchronized even without any beacons.

TECHNICAL FIELD

The present invention relates to a radio communication network, and moreparticularly to ad hoc network communication in a mobile environment.

BACKGROUND ART

In recent years, various proposals have been made concerning UWB (UltraWide Band) radio communication methods. As UWB radio communication isbroadband communication exceeding 1 Gbps, its application to videotransmission and the like with large transmission capacity has beeninvestigated. On the other hand, UWB cannot be said to be easy to use inan office environment due to the narrowness of its possiblecommunication range, and it can be said to be better suited to PANs(Personal Area Networks) that are attracting attention nowadays.However, PANs are still in their early days, and there are very fewmajor applications. This is because a device exploiting the broadbandcharacteristics generally uses a lot of power, but in the case of a PAN,movement is difficult while carrying a large number of batteries.

One application that uses a PAN and requires the broadbandcharacteristics of UWB is a file exchange (file-swapping, file-sharing)application. The basic operating principle of a file exchangeapplication is disclosed in Patent Document 1, for example. It ispossible to create a mini-community with random file exchange in amobile environment (referred to as message exchange in Patent Document1). Although not mentioned in Patent Document 1, exchanged data is notlimited to text documents, and the exchange of music, image, video, andsuchlike files is also possible. With UWB in particular, since theeffective transmission speed is 100 Mbps to several Gbps, it is possibleto exchange large files that bypass each other, and this kind of fileexchange can be said to be an application suited to UWB.

Various discussions concerning transmitting methods used in this UWBhave emerged in IEEE802.15. There are many cases in which a MAC protocolimplemented in a PAN (and more particularly, a mobile PAN) environmentis a method using autonomous distributed processing. This is because, ina PAN environment in which terminals constantly pass by each other,constructing a master-slave relationship each time, and startingcommunication after setting up a communication environment, such asassigning data slots, is a major overhead.

Non-patent Document 1 discloses a radio communication method in anautonomous distribution type PAN.

FIG. 1 is a drawing showing the configuration of a super-frame in TDMA(Time Division Multiple Access).

In FIG. 1, a super-frame is divided into a beacon period 2201 and a dataperiod 2202.

Beacons 2203 are transmitted from radio communication apparatuses withinbeacon period 2201, and it is guaranteed that beacons of neighbor nodespropagate to neighbor nodes without colliding.

Data period 2202 is divided equally into slots 2204, and slot IDs areassigned in that order, but this is not a limitation, and data periodsmay be unequal, and need not be contiguous.

Patent Document 1: Unexamined Japanese Patent Publication No.2001-298406

Non-patent Document 1: “Towards High Speed Wireless Personal AreaNetwork-Efficiency Analysis of MBOA MAC”, Yunpeng Zang, et al, InternetURL: http://www.ctr.kcl.ac.uk/IWWAN2005/papers/88_invited_Philips.pdf

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, in the case of the radio communication method described inNon-patent Document 1, if there are mixed super-frame groups that sharea beacon period, data slot and beacon period collisions may occur.

One possible method of solving this problem is for all nodes belongingto a PAN to constantly detect super-frame group collisions, and tocompose an algorithm that adapts to this in a distributed fashion.

However, with the above-described method, it is necessary for a radiocommunication apparatus to keep its beacon receiving section in areception wait (standby) state at all times, and reception standby poweris large. This is difficult to allow in UWB communication, and is amajor demerit in an environment in which power can only be expected tobe supplied by a battery, as in the case of a mobile communicationapparatus.

Also, since a radio communication apparatus must constantly emit abeacon regardless of whether or not there are other radio communicationapparatuses in the vicinity, power consumption is further increased.

It is an object of the present invention to provide a radiocommunication method and radio communication apparatus that enable powerconsumption to be reduced as compared with a conventional case, and asuper-frame to be synchronized with the super-frame of another radiocommunication apparatus, in an ad hoc network.

Means for Solving the Problems

A radio communication method of the present invention is a radiocommunication method whereby a plurality of radio communicationapparatuses communicate with each other in an ad hoc network, and has astep of transmitting an end tone for identifying the end of asuper-frame from one radio communication apparatus, and a step ofsynchronizing at another radio communication apparatus, the end of itsown super-frame when having received that end tone.

By this means, a radio communication apparatus performs synchronizationwith a super-frame by using a low-power-consumption tone signal, withoutusing a beacon provided by a modulated signal, enabling powerconsumption to be reduced as compared with a conventional method.

Also, a radio communication apparatus of the present invention has atone signal communication section that transmits and receives tonesignals, a data signal communication section that performs modulationand transmits and receives data by means of a broadband signal, a timemanagement section, and a frame transmitting/receiving section. Thistime management section measures elapsed time in a super-frame,transmits an end tone for identifying the end from the tone signalcommunication section, or receives an end tone from the tone signalcommunication section, and re-sets the end time based on the end tonereceived first before its own end time. The frame transmitting/receivingsection transmits a send/receive tone for giving notification of datatransmission from the tone signal communication section after the elapseof a predetermined time based on the end time re-set by the timemanagement section, and after transmission of that send/receive tone iscompleted, transmits data from the data signal communication section, orsets the data signal communication section to a reception-enabled statewhen a send/receive tone is received, and receives data from the datasignal communication section.

By means of this configuration, the radio communication apparatus canimplement super-frame synchronization between super-frame groups withoutusing a beacon.

ADVANTAGEOUS EFFECT OF THE INVENTION

According to the present invention, in an ad hoc network a radiocommunication apparatus can reduce stand by power consumptionas comparedwith a conventional case, and super-frame synchronization adjustmentbecomes possible in a mobile environment. As a result, communicationwith another radio communication apparatus can be started in a minimaltime.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a drawing showing the configuration of a TDMA super-frame in aconventional radio communication method;

FIG. 2 is a drawing showing the configuration of a radio communicationapparatus according to Embodiment 1 of the present invention;

FIG. 3 is a timing chart showing a tone signal and frametransmission/reception protocol according to Embodiment 1 of the presentinvention;

FIG. 4 is a drawing showing the length of each tone signal according toEmbodiment 1 of the present invention;

FIG. 5 is a flowchart explaining super-frame synchronization processingaccording to Embodiment 1 of the present invention;

FIG. 6 is a drawing showing a super-frame synchronization operationaccording to Embodiment 1 of the present invention;

FIG. 7 is a drawing showing the arrangement of two super-frame groupsaccording to Embodiment 1 of the present invention;

FIG. 8 is a flowchart explaining super-frame re-synchronizationprocessing according to Embodiment 1 of the present invention;

FIG. 9 is a drawing showing a re-synchronization end tonetransmission/reception operation of a radio communication apparatusaccording to Embodiment 1 of the present invention;

FIG. 10 is a drawing showing a data transmission/reception operationaccording to Embodiment 1 of the present invention;

FIG. 11A is a flowchart explaining probe processing of a request-sideradio communication apparatus according to Embodiment 1 of the presentinvention, and FIG. 11B is a flowchart explaining probe processing of aresponse-side radio communication apparatus according to Embodiment 1 ofthe present invention;

FIG. 12A is an arrangement drawing of a case in which radiocommunication apparatuses according to Embodiment 1 of the presentinvention are located within two hops, FIG. 12B is a drawing showingbeginning tone 1 and 2 transmission/reception operations of radiocommunication apparatuses according to Embodiment 1 of the presentinvention, and FIG. 12C is a drawing showing beginning tone 1 and 2transmission/reception operations of radio communication apparatusesaccording to Embodiment 1 of the present invention;

FIG. 13A is an arrangement drawing of a case in which radiocommunication apparatuses according to Embodiment 1 of the presentinvention are located within three hops, and FIG. 13B is a drawingshowing beginning tone 1 and 2 transmission/reception operations ofradio communication apparatuses according to Embodiment 1 of the presentinvention;

FIG. 14 is a drawing showing operations when a radio communicationapparatus according to Embodiment 1 of the present invention receives atone signal;

FIG. 15 is a drawing showing operations when a radio communicationapparatus according to Embodiment 1 of the present invention receives atone signal;

FIG. 16 is a drawing explaining collision avoidance by means of RTS/CTSaccording to Embodiment 1 of the present invention;

FIG. 17 is a block diagram showing an arrangement of radio communicationapparatuses according to Embodiment 2 of the present invention;

FIG. 18 is a timing chart explaining the super-frame tone signals andframe according to Embodiment 3 of the present invention;

FIG. 19 is a drawing showing the configuration of a radio communicationapparatus according to Embodiment 3 of the present invention;

FIG. 20A is an operation flowchart of a probe-request-source radiocommunication apparatus according to Embodiment 3 of the presentinvention, and FIG. 20B is an operation flowchart of a probe-respondingradio communication apparatus according to Embodiment 3 of the presentinvention;

FIG. 21 is a drawing showing the configuration of a mobile file exchangeapparatus according to Embodiment 4 of the present invention;

FIG. 22 is a drawing showing the configuration of a music software filelist managed by a mobile file exchange apparatus according to Embodiment4 of the present invention;

FIG. 23 is a drawing showing the configuration of a mobile file exchangeapparatus according to Embodiment 5 of the present invention;

FIG. 24 is a drawing showing a sequence whereby a mobile file exchangeapparatus according to Embodiment 5 of the present invention connects toan access point;

FIG. 25 is a block diagram showing the configuration of a signalcommunication section according to Embodiment 6 of the presentinvention;

FIG. 26 is a block diagram showing the configuration of a signalcommunication section according to Embodiment 7 of the presentinvention; and

FIG. 27 is a timing chart showing signal waveforms of a signalcommunication section according to Embodiment 7 of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described withreference to the accompanying drawings. In the following embodiments,radio communication apparatuses are assumed to perform datacommunication procedures by means of millimeter wave UWB.

Embodiment 1

FIG. 2 is a configuration diagram of a radio communication apparatusaccording to this embodiment of the present invention.

In FIG. 2, the radio communication apparatus is equipped with an antenna105, a directivity control section 106, a broadband communicationsection 101, a narrowband communication section 102, a MAC controlsection 103, and an upper layer processing section 104.

Antenna 105 comprises a plurality of directional antennas eachresponsible for a particular sector, and directivity control section 106controls the directional antennas composing antenna 105 and determinesthe communication range. Broadband communication section 101 transmitsand receives UWB signals, and narrowband communication section 102transmits and receives narrowband signals with or without performingmodulation. If a broadband signal is DS-UWB (Direct Sequence UWB), therespective transmitters may be shared so as to widen the transmittedDS-UWB pulse width in order to transmit a narrowband signal.

Upper layer processing section 104 executes various kinds ofapplications, generates transmit data such as content data and sendsthis to MAC control section 103, and also receives receive data from MACcontrol section 103 and performs application processing.

MAC control section 103 performs MAC protocol processing, and has aframe transmitting/receiving section 131, a time management section 132,a re-synchronization control section 133, a beginning tone controlsection 134, an RTS/CTS-e data frame transmitting section 135, a probereceiving section 136, and a probe transmitting section 137.

Frame transmitting/receiving section 131 transmits and receives asend/receive tone giving notification of data communication, andtransmits/receives a subsequent frame by means of a narrowband signalusing an RTS/CTS (Ready to Send/Clear to Send) extended method(RTS/CTS-e method) described later herein.

Time management section 132 manages time from the start time of asuper-frame, and measures the transmission time of an end tone thatgives notification of the end of its own super-frame, and also performstiming exchange with narrowband communication section 102 in order toperform synchronization with the end tone of another node (such as aradio communication apparatus).

Re-synchronization control section 133 transmits a re-synchronizationsignal via narrowband communication section 102 in order to synchronizewith another super-frame group. Also, re-synchronization control section133 monitors end tones over the entire super-frame range, and reportsthe timing of synchronization with another super-frame to timemanagement section 132.

Beginning tone control section 134 transmits or receives a beginningtone 1 or beginning tone 2 for avoiding a data communication collisionin accordance with a CSMA/CA (Carrier Sense Multiple Access withCollision Avoidance) procedure with a tone as a carrier.

RTS/CTS-e data frame transmitting section 135 generates a frame fortransmitting data received from upper layer processing section 104, andsends this to frame transmitting/receiving section 131. RTS/CTS-e dataframe transmitting section 135 also generates an RTS command of theRTS/CTS extended method (RTS/CTS-e method) described later herein, andsends this to frame transmitting/receiving section 131.

Probe receiving section 136 receives a probe request from another radiocommunication apparatus, generates information such as its ownattributes and communication environment, and responds to the requestingnode. This probe request asks the request destination for informationsuch as the attributes and communication environment of that node.

Probe transmitting section 137 generates a probe request for requestinginformation such as the attributes and communication environment of aneighbor node, and transmits this to a neighbor node. Also, on receivinga probe response from a probe request destination node, probetransmitting section 137 transmits “probe end” as a response.

Various kinds of tone signals and frames according to the presentinvention will now be described. First, a definition of a tone signalwill be given. Here, a tone signal denotes an electrical signal that isidentified by continuous transmission for a determined time withoutregard to narrowband signal modulation/non-modulation. The configurationclosely resembles a busy tone used to convey to a neighbor node a statein which a signal is being emitted, such as in BTMA (Busy-Tone MultipleAccess) or DBTMA (Dual Busy-Tone Multiple Access), for example.

FIG. 3 is a timing chart showing a transmission/reception protocol forthis tone signal and frame.

In FIG. 3, a super-frame 221 is divided into end tone slots 222, a probeslot 223, and a data period 224.

An end tone slot 222 is a period in which end tones (END) 201 and 202are transmitted and received. Probe slot 223 is a period in whichbeginning tone 1 (BT1) 203, beginning tone 2 (BT2) 204, probe request(PB) 211, probe response (PR) 212, acknowledge (PACK) 213, and probe end(PE) 214, are transmitted and received. Data period 224 is a period inwhich send/receive tones (SR) 205 and 206, data 215, and ACK/NACK 216,are transmitted and received.

FIG. 4 is a drawing showing the length of each tone signal. That is tosay, beginning tone 1 duration T2 is twice the length of send/receivetone duration T1, beginning tone 2 duration T3 is twice the length ofbeginning tone 1 duration T2, and end tone duration T4 is twice thelength of beginning tone 2 duration T3. Beginning tone 2 duration T3must be no more than half the length of end tone duration T4, but apartfrom this the above ratios need not be maintained, and it is onlynecessary for the relationships of the length to be maintained. This isbecause even if two or more beginning tones 2 are detected, detection asbeginning tone 2 is necessary. The occurrence of three or more beginningtones 2 in series, resulting in a multiple of two or more, is judged tobe extremely rare.

For example, when a send/receive tone is stipulated as being 10microseconds in length, on receiving a tone signal, narrowbandcommunication section 102 determines a tone signal whose duration isless than 10 microseconds to be a send/receive tone. Narrowbandcommunication section 102 determines a tone signal from 10 microsecondsto the beginning tone 1 duration to be beginning tone 1. Furthermore,narrowband communication section 102 determines a tone signal from thebeginning tone 1 duration to the beginning tone 2 duration to bebeginning tone 2, and determines a tone signal of greater duration to bean end tone.

The operation and action of a radio communication apparatus configuredas described above will now be explained.

First, super-frame synchronization processing will be described.

FIG. 5 is a flowchart explaining super-frame synchronization processing.

In FIG. 5, first, if there is no notification of detection of an endtone of another node from narrowband communication section 102 (stepS401), time management section 132 checks whether or not it is time totransmit the apparatus's own end tone (step S402).

If it is not time to transmit the apparatus's own end tone, theprocessing flow returns to step S401, whereas if it is time to transmit,time management section 132 directs narrowband communication section 102to transmit the apparatus's own end tone. Narrowband communicationsection 102 receives this directive, transmits an end tone (step S403),and proceeds to the processing in step S408 described later herein.

On the other hand, if narrowband communication section 102 detects anend tone from another node, it notifies time management section 132.Time management section 132 checks whether or not the present end tonedetection was prior to the apparatus's own end tone output, and wasreported first in the current end tone slot (step S404). Then, if theend tone is not first, time management section 132 performsre-synchronization processing described later herein (step S405) andterminates the processing.

On the other hand, if the end tone was reported first, time managementsection 132 sets the start time of super-frame period managed by itselfto the current time (step S406).

Next, time management section 132 checks whether or not the notificationfrom narrowband communication section 102 reports the end of an end tonefrom another node (step S407).

If this is not the end of an end tone, narrowband communication section102 returns to step S402, whereas if this is the end, narrowbandcommunication section 102 proceeds to step S403 and performs processingto transmit the apparatus's own end tone (step S403). After the end ofend tone transmission, time management section 132 performs confirmationas to whether or not its own end tone slot period has ended (step S408).If its own end tone slot period has ended, processing is terminated. Ifits own end tone slot period has not ended, the processing flow returnsto step S401.

Thus, time management section 132 transmits end tone 201 when itmeasures the end tone output time, but if it detects end tone 202transmitted from another neighbor node within the end tone slot 222range, measures the time difference from its own end tone 201. Then timemanagement section 132 sets its own super-frame end time to the starttime of end tone 202 detected earlier than its own.

With regard to time management section 132, neighbor nodes also transmitan end tone within the same end tone slot 222, but all nodes set theirown end tone start times to the end tone transmission start time of thenode that transmits the earliest end tone among these. If theapparatus's own end tone transmission start time arrives duringreception of the earliest end tone transmitted from another node, an endtone is transmitted, but if end tone reception is completed before theapparatus's own end tone transmission start time, the apparatus's ownend tone is transmitted at that point in time.

By this means, it is possible for each node to synchronize with theearliest end tone in a super-frame.

Then, based on the start time of this synchronized super-frame 221, timemanagement section 132 measures the timing of probe slot 223 and a dataslot within data period 224. Assuming that a super-frame is defined as64 ms, and the length of end tone slot 222 as 512 microseconds, timemanagement section 132 transmits an end tone after the elapse of 256microseconds, which is the midway point of end tone slot 222. This is toallow accommodation in end tone slot 222 of another radio communicationapparatus even if the end tone start time of this apparatus varies.

This super-frame synchronization operation will now be described usingan actual example.

FIG. 6 is a drawing showing the operation whereby each radiocommunication apparatus of the same super-frame group synchronizes asuper-frame period. The ellipses in the drawing indicate thecommunication capability areas of the radio communication apparatuses.Radio communication apparatus A through radio communication apparatus Gare assumed to be mutually contiguous as shown in the drawing. In FIG.6, an upper signal of each radio communication apparatus indicatesreception, and a lower signal indicates transmission.

In FIG. 6, radio communication apparatus B performs transmission of anend tone 502 at end tone sending timing of a super-frame period, butdetects an end tone 501 of radio communication apparatus A beforetransmission of its own end tone 502, and therefore sets its ownmeasured super-frame period start timing to super-frame period starttiming 501 of radio communication apparatus A. Similarly, radiocommunication apparatus C synchronizes its own super-frame start timewith end tone 502 of radio communication apparatus B. By this means, thedelay times of radio communication apparatus B and radio communicationapparatus C are gradually absorbed into the delay times specific totheir own super-frame periods.

Synchronization processing is also performed in a similar way for radiocommunication apparatuses D through F, synchronization being performedwith the super-frame of the radio communication apparatus that transmitsan end tone earliest within its own communication capability area.

End tone transmission time 503 of radio communication apparatus G isafter the transmission of end tone 504 of radio communication apparatusF, and therefore the radio communication apparatus G end tone istransmitted from the time at which radio communication apparatus Fcompletes transmission of end tone 504. Then, in the next super-frame,radio communication apparatus G catches up with the super-frame starttiming of the other radio communication apparatuses.

A description will now be given of super-frame re-synchronizationprocessing in the case of mixing with another super-frame group.

In this super-frame re-synchronization processing, a radio communicationapparatus performs end tone detection for super-frames as a whole, andwhen an end tone of another super-frame group is detected, synchronizeswith a super-frame of another super-frame group that transmitted an endtone earliest.

FIG. 7 is a drawing showing a case in which radio communicationapparatuses 601 through 603 compose a super-frame group, and radiocommunication apparatuses 604 through 606 compose a separate super-framegroup. In FIG. 7, radio communication apparatus 604 and radiocommunication apparatus 606 are within the communication capability areaof radio communication apparatus 603.

If radio communication apparatus 603 detects an end tone of anothersuper-frame group outside an end tone slot at such a time, radiocommunication apparatus 603 and radio communication apparatuses of thesame super-frame group perform re-synchronization processing taking thatas the starting point, and ultimately radio communication apparatuses601 through 606 come to share the same super-frame.

FIG. 8 is a flowchart that determines whether or not super-framere-synchronization processing is started at the end of end tonetransmission/reception.

In FIG. 8, re-synchronization control section 133 checks whether or notthe apparatus has received an end tone in a transmit/receive slot or thelike in a super-frame period (step S701). If an end tone has beenreceived, re-synchronization control section 133 checks whether or notthis is a node for which the super-frame synchronization count since theapparatus finished the previous re-synchronization processing is greaterthan or equal to a predetermined number (designated count N) andre-synchronization is to be performed (step S702) If thissynchronization count is large, the number of times reception is awaitedfor super-frames as a whole is reduced and a power consumption isreduced accordingly, but the start of communication with another groupis delayed. Generally, a synchronization count giving a rate of aroundonce per second is desirable. Then, if this condition is met,re-synchronization control section 133 transmits a re-synchronizationend tone regardless of another node (step S703). This re-synchronizationend tone is an end tone transmitted again when 10-plus microseconds haveelapsed from the end of the apparatus's own super-frame group end tonetransmission, and notifies another node of the start ofre-synchronization processing. Following this, re-synchronizationcontrol section 133 performs re-synchronization processing (step S704).Here, re-synchronization processing is processing that performsreception of end tones to be synchronized across super-frames as awhole. A node that receives this re-synchronization end tone but whosesuper-frame synchronization count has not reached predetermined count Nresets the super-frame count, relays the re-synchronization end tone,and enters a re-synchronization state.

If, in step S701, the apparatus has received an end tone in asuper-frame, re-synchronization control section 133 transmits are-synchronization end tone (step S703). Then, in order to synchronizespeedily, re-synchronization processing is initiated (step S704).

In the above example the wait time until a re-synchronization end toneis transmitted is 10-plus microseconds, but this depends on the lengthof the end tone. Normally, nodes of the same super-frame group do nottransmit an end tone in a time period three times the length of the endtone or more, and therefore a super-frame should be transmitted after agap of around this triple time period. However, if the distance is toogreat there is a possibility of an end tone of a different super-framegroup being erroneously mixed with the re-synchronization end tone, andtherefore this point must also be taken into consideration.

FIG. 9 is a drawing showing an operation whereby a radio communicationapparatus that has detected another super-frame group performsre-synchronization end tone transmission/reception. As in FIG. 6, radiocommunication apparatus A through radio communication apparatus G arecontiguous as shown in the drawing. In FIG. 9, an upper signal of eachradio communication apparatus indicates reception, and a lower signalindicates transmission. Here, radio communication apparatus D detectsthe existence of another super-frame group, and transmits are-synchronization end tone 801. Peripheral super-frame group radiocommunication apparatuses C and E relay the received re-synchronizationend tone by means of re-synchronization end tones 802 and 803. However,in the case of radio communication apparatus A and radio communicationapparatus G, the end tone slot ends before those re-synchronization endtones 804 and 805 are relayed to them, and therefore radio communicationapparatus A and radio communication apparatus G do not enter are-synchronization state.

However, radio communication apparatuses A and G transmit are-synchronization end frame in the next super-frame so as tosynchronize with end tones output in synchronization by radiocommunication apparatuses B through F, and a single synchronizationtiming is achieved overall.

This concludes a description of super-frame re-synchronizationprocessing.

Next, data transmission/reception operation will be described.

First, after generating a data frame, RTS/CTS-e data frame transmittingsection 135 gives a directive for data frame transmission to frametransmitting/receiving section 131. On receiving this, frametransmitting/receiving section 131 transmits send/receive tone 205 vianarrowband communication section 102. After completion of send/receivetone 205 transmission, frame transmitting/receiving section 131transmits data in a narrowband signal via broadband communicationsection 101.

By this means, a node in a frame wait state always need only wait for anarrowband signal, and standby is possible with lower power consumptionthan when always waiting for a broadband signal.

FIG. 10 is a drawing showing this data transmission/reception operation.

Radio communication apparatus A transmits a data frame to radiocommunication apparatus B and receives a corresponding acknowledge frame(ACK). Both enter a reception wait state unless transmitting anarrowband signal. Radio communication apparatus A transmits asend/receive tone (SR) 901 before data 902 transmission, and onreceiving this, radio communication apparatus B transits to a narrowbandsignal reception wait state (S911). Similarly, after radio communicationapparatus B sends a send/receive tone (SR) 903, it transmits ACK 904.This send/receive tone is transmitted before transmission of any frame.

Next, a description will be given of probe processing for acquiring thecommunication state of a neighbor node.

When starting communication, a radio communication apparatus needs toascertain the existence and address of the communicating party. Also, toprevent send/receive signal from colliding with a communication signalfrom another node, it is necessary to check the existence of neighbornodes. For this purpose, in this embodiment the attributes,communication environment, and so forth, of a neighbor node are acquiredusing a probe command.

Probe slot 223 can only be used for probe transmission/reception, butits length can be changed dynamically as necessary. If there is no probetransmission request, it is also possible to terminate the probe slot atthat point in time. However, with a probe slot, a radio communicationapparatus can only perform transmission/reception of one set of probesin one super-frame, and therefore there is a possibility of a pluralityof requests colliding. Beginning tones 1 (203, 209) and beginning tones2 (204, 210) are used to solve this problem.

When multicasting is performed, the system is normally prepared forcollision with a node located next to the neighbor node when carryingout transmission, but when beginning tones 1 and 2 are used, each nodecategorizes itself as a probe-request-source node, a probe responsenode, or a silent node in order to prevent a collision.

FIG. 11A is a flowchart explaining probe processing of a request-sideradio communication apparatus, and FIG. 11B is a flowchart explainingprobe processing of a response-side radio communication apparatus.

In FIG. 11A, first, probe transmitting section 137 of a probe-requestingnode performs tone signal carrier sense, and when this is cleared, givesa directive for transmission of beginning tone 1 (BT1) 203 to beginningtone control section 134. Beginning tone control section 134 transmitsbeginning tone 1 (203) via narrowband communication section 102 at thepoint in time at which the end tone slot ends (step S101). At this time,narrowband communication section 102 transmits beginning tone 1. Thenthe node that has completed transmission of beginning tone 1 placesbroadband communication section 101 in the “power on” state in thisprobe slot (step S102), and operates as a requesting node.

On the other hand, in FIG. 11B, narrowband communication section 102 ofa node not making a probe request is in a tone signal reception state,and on receiving beginning tone 1 (step S121), notifies beginning tonecontrol section 134. Beginning tone control section 134 receives thisnotification and transmits beginning tone 2 (BT2) 204 (step S122). Then,this node that received beginning tone 1 places broadband communicationsection 101 in the “power on” and driving state in current probe slot223 (step S123), and operates as a responding node. On receivingbeginning tone 1, narrowband communication section 102 of a nodeplanning a probe request becomes a responding node, and stops beginningtone 1 transmission.

A node that receives beginning tone 2 transmitted from a node thatreceived beginning tone 1 (step S131) keeps broadband communicationsection 101 in the “power off” state during that probe slot 223 andoperates as a silent node.

Next, in FIG. 11A, beginning tone control section 134 of the requestingnode checks reception of beginning tone 2 (step S103), and on receivingconfirmation, notifies probe transmitting section 137. Probetransmitting section 137 receives this notification and sends a proberequest frame to frame transmitting/receiving section 131. Frametransmitting/receiving section 131 receives this, places broadbandcommunication section 101 in the “power on” state, and transmits proberequest (PB) 211 via broadband communication section 101 (step S104).

On the other hand, in FIG. 11B, on receiving the probe request frame(step S124), broadband communication section 101 of the responding nodesends that frame to frame transmitting/receiving section 131. Ondetermining that the received frame is a probe request, frametransmitting/receiving section 131 notifies probe receiving section 136.Probe receiving section 136 receives this notification, and generatesinformation on its apparatus's attributes and communication environment(step S125). Then probe receiving section 136 sends a directive to frametransmitting/receiving section 131 to transmit a probe responsecontaining these items of information. Frame transmitting/receivingsection 131 receives this and transmits probe response (PR) 212 viabroadband communication section 101 (step S126).

At this time, frame transmitting/receiving section 131 applies back-offand responds at random timing in order to prevent a collision with proberesponse (PR) 212 transmitted from another responding node. Back-offhere refers to a method whereby the timing at which retransmission isperformed when a collision is detected is calculated more randomly, andretransmission is performed after the elapse of the calculated time.

Before transmitting probe response 212 by means of broadbandcommunication, frame transmitting/receiving section 131 transmits asend/receive tone 207 in the same way as in ordinary frame transmission.

In the case of a silent node, broadband communication section 101 is inthe “power off” state, and therefore broadband communication section 101does not receive a probe request or probe response.

Next, in FIG. 11A, narrowband communication section 102 of therequesting node relays send/receive tone 207 at the point in time atwhich it receives this send/receive tone 207. By this means, a radiocommunication apparatus that started a response (responding node) and aresponding node on the opposite side via the probe requester can beprevented from starting to transmit response probe at the same time. Asa result, normally performed collision avoidance processing by means ofRTS/CTS can be greatly shortened.

Then, on receiving a probe responding frame (step S105), requesting nodebroadband communication section 101 sends this to frametransmitting/receiving section 131. On determining that the receivedframe is a probe request, frame transmitting/receiving section 131notifies probe transmitting section 137. Probe transmitting section 137receives this notification, and stores and updates it as neighbor nodeattribute and communication environment information (step S106).

Next, probe transmitting section 137 gives a directive to frametransmitting/receiving section 131 for ACK or NACK transmission as aresponse to the probe response. After frame transmitting/receivingsection 131 sends a send/receive tone 208 via narrowband communicationsection 102, frame transmitting/receiving section 131 transmits an ACKor NACK frame via broadband communication section 101 (step S107).

On the other hand, in FIG. 11B, on receiving this ACK or NACK response(step S127), the responding node enters a state of waiting for receptionof “probe end” giving notification of the end of the probe slot.

Also, another responding node that receives this ACK or NACK responseand has not transmitted a probe response restarts a back-off countdown.Then that responding node performs probe response transmission aftercompletion of the countdown (step S126).

On the other hand, in FIG. 11A, probe request node probe transmittingsection 137 returns to step S105 until completion of the maximumback-off count started after probe request transmission (step S108), andperforms reception processing of a response probe from anotherresponding node. This maximum back-off count counts a predetermined timeperiod in consideration of a back-off response, and probe transmittingsection 137 considers a probe slot to have ended when this maximumback-off count is completed. Probe request node probe transmittingsection 137 halts the same countdown as the responding node duringreception of a probe response, and if a collision should occur duringback-off, begins a maximum back-off countdown anew. By this means,sufficient time can be secured to enable a responding node to respondwithout fail, and when the number of responding nodes is small, probetermination can be performed with a correspondingly short wait time.

Following this, probe request node probe transmitting section 137transmits a probe end frame to report the end of the probe slot. At thistime, probe transmitting section 137 gives a directive for transmittingbeginning tone 1 again to beginning tone control section 134. Beginningtone control section 134 transmits beginning tone 1 (209) via narrowbandcommunication section 102 in the same way as in step S101 (step S109).By this means, a silent node with in a two-hop area can return to normaltransmit/receive mode.

Then, in the same way as in step S103, when beginning tone controlsection 134 receives beginning tone 2 (210) (step S110), probetransmitting section 137 gives a directive for “probe end” transmissionto frame transmitting/receiving section 131. Frametransmitting/receiving section 131 receives this, transmits probe end(PE) 214 via broadband communication section 101 (step S111), andterminates this probe slot.

On the other hand, in FIG. 11B, on receiving beginning tone 1 (stepS128), responding node beginning tone control section 134 transmitsbeginning tone 2 (step S129), and after transmission is completed, frametransmitting/receiving section 131 receives probe end (214) (step S130)and regards this as the end of the probe slot. Thus, when probeprocessing is performed, if two or more nodes transmit beginning tone 1within a one-hop area, one or the other can transmit by means of carriersense, and the other(s) wait(s) for reception.

Probe operations will now be described using an actual example.

FIG. 12 shows beginning tone 1 and 2 transmission/reception operationswhen radio communication apparatuses A through D are located within twohops.

In FIG. 12A, radio communication apparatus A and radio communicationapparatus D are assumed to be nodes that make probe requests. At thistime, as shown in FIG. 12B, radio communication apparatus A firsttransmits a beginning tone 1 (1101), and after transmission of thatbeginning tone 1 is completed, radio communication apparatus D preparesto transmit beginning tone 1 and performs carrier sense. In this case,since radio communication apparatuses B and C are already transmitting abeginning tone 2 (1102) in response to beginning tone 1 (1101) fromradio communication apparatus A, radio communication apparatus Dreceives beginning tone 2 (1102) during carrier sense or before carriersense, and therefore makes itself a silent node. Therefore, radiocommunication apparatus A acquires the probe request transmission right.

Next, as shown in FIG. 12C, when beginning tone 1 transmission by radiocommunication apparatus A and beginning tone 1 transmission by radiocommunication apparatus Dare performed with a difference of the durationof beginning tone 1 or less, radio communication apparatuses B and Creceive a tone signal 1110 longer than the duration of beginning tone 1and shorter than the duration of an end tone. Consequently, radiocommunication apparatuses B and C determine the received tone signal tobe beginning tone 2. Therefore, radio communication apparatuses B and Cbecome silent nodes, and do not give a response in the current probeslot. Radio communication apparatuses B and C cannot participate inprobe processing, but do not interfere with radio communicationapparatus A and D communications due to becoming silent nodes.

Thus, by means of probe processing using beginning tones 1 and 2 of thepresent invention, each radio communication apparatus can become anappropriate node (requesting node, responding node, or silent node) in aprobe slot.

Next, operations when two or more nodes perform probe requests within athree-hop area will be described.

FIG. 13 shows beginning tone 1 and 2 transmission/reception operationswhen radio communication apparatuses A through E are located withinthree hops.

In FIG. 13A, radio communication apparatuses A and E are assumed to benodes that make probe requests. At this time, as shown in FIG. 13B,radio communication apparatus A first transmits a beginning tone 1(1201), and at timing prior to completion of transmission of thatbeginning tone 1, a beginning tone 1 (1203) is transmitted from radiocommunication apparatus E. In this case, radio communication apparatusesB and C receive beginning tone 1 (1201) only from radio communicationapparatus A, and therefore transmit a beginning tone 2 (1202) inresponse thereto. Therefore, radio communication apparatus D startsreceiving beginning tone 2 (1202) during reception of beginning tone 1(1203) from radio communication apparatus E, and so receives a tonesignal 1210 longer than the duration of beginning tone 1 and shorterthan the duration of an end tone. Consequently, radio communicationapparatus D determines the received tone signal to be beginning tone 2,and becomes a silent node.

Thus, according to probe processing of the present invention, even if aplurality of probe processing occurs virtually simultaneously, one probeprocessing is allowed to succeed, and the other probe request node issilenced, enabling both probe requests to proceed smoothly withoutcolliding.

Only one probe request is executed in a probe slot, but a silent nodemay also receive a plurality of beginning tones 2. In this case, thesilent node cannot return to the normal standby state unless beginningtone 2, which is to be received before “probe end” is transmitted, isreceived the number of times beginning tone 2 is received. If twobeginning tones 2 are not received for some reason, the silent noderemains silent for the maximum back-off count period.

The above description is summarized in FIG. 14 and FIG. 15.

FIG. 14 and FIG. 15 show operations of a radio communication apparatusaccording to the present invention when a tone signal is received.

In FIG. 14 and FIG. 15, each row shows a super-frame slot, and eachcolumn shows a received tone signal. For example, it is shown that whenbeginning tone 1 is received in a probe slot before probe requestreception, beginning tone 2 is transmitted, and broadband signalsynchronization is started to receive a probe request.

According to the present invention, a MAC protocol can be used that isrestricted so that only an apparatus that performstransmission/reception transmits a beacon or suchlike management commandframe. That is to say, an apparatus that does not performtransmission/reception need not transmit a beacon or the like as a sleepstate mode.

Furthermore, according to this embodiment, RTS/CTS is a method thatextends conventional RTS/CTS (the RTS/CTS-e method).

With the RTS/CTS method, originally a radio communication apparatustransmits data using the band immediately after transmitting therelevant command frame, but in this embodiment, a data transmission timeperiod is reserved by specifying a time up to a specifiable time (forexample, 64 ms). This provides a substitute for TDMA time reservation.

Also, when a radio communication apparatus performs reservationsconsecutively, a slot for the next RTS/CTS-e exchange is also reserved.By this means, it is also possible to support isochronous communicationand so forth.

In this embodiment, the RTS/CTS-e method is a 4-way handshake method.That is to say, in the initial handshake, free time of the communicatingparty is confirmed, and in the next RTS/CTS-e handshake the actualtransmission time is confirmed and reported in the surrounding area.

The reason for using this 4-way method is that suppressing RTS/CTS-eupdating by another radio communication apparatus with an NAV (NetworkAllocation Vector) enables the latest communicating-party schedule atthe present point in time to be confirmed.

Reserved time specification methods are actual time specification andslot specification in line with synchronization timing. With the slotspecification method, by adding time up to the start time of one's ownnext super-frame period, determination of a slot position is possibleeven in the event of a collision with another super-frame group. Then, acollision with another super-frame group can be avoided by prohibitingthe use of one's own super-frame group slot position corresponding to aslot of that other super-frame group.

Thus, as compared with the actual time specification method, the slotspecification method enables the amount of data communicated to bereduced, but on the other hand incurs the possibility of taking moretime than necessary. However, it does not matter which of thespecification methods is used.

Using millimeter wave UWB enables directivity to be utilized. That is tosay, frame transmitting/receiving section 131 transmits a series of tonesignals and RTS/CTS frames by means of a non-directional radio wave.Then, when performing actual data, ACK, or suchlike transmission, frametransmitting/receiving section 131 predicts the direction of arrival ofa radio wave when RTS/CTS is received, and when actually transmittingdata, transmits or receives a directional radio wave in the predicteddirection of arrival.

FIG. 16 is a drawing explaining collision avoidance when a radiocommunication apparatus transmits RTS/CTS by means of a non-directionalradio wave and estimates the direction of arrival of RTS/CTS for dataexchange.

In FIG. 16, if radio communication apparatus B transmits data by meansof a directional radio wave when radio communication apparatus D istransmitting RTS by means of a non-directional radio wave, communicationarea 1302 of radio communication apparatus B does not include radiocommunication apparatus C. Therefore, data radio wave 1301 does notreach radio communication apparatus C, and does not interfere with RTSreception.

By having a beacon or RTS/CTS-e exchange not performed other than by aradio communication apparatus that performs transmission/reception inthis way, unnecessary transmission/reception in a mobility environmentcan be avoided. Furthermore, it also becomes possible to startcommunication at any time while constantly checking surrounding radiocommunication apparatuses.

For tone signals of this embodiment, individual tones have beenidentified by differences in duration, but this is not a limitation, andthe same kind of effect can also be achieved by means of differencesinfrequency, relative magnitudes of field strength, temporalfluctuations in field strength, intermittent signal patterns, and soforth.

As described above, according to the present invention, by using a tonesignal instead of a beacon it is possible for a radio communicationapparatus to perform time adjustment within a super-frame withoutperforming frequent beacon arrangement in a mobility environment. Bythis means, a radio communication apparatus can perform probe requestsand responses vis-à-vis another radio communication apparatus in aminimal time. Also, since only a communicating radio communicationapparatus need place its broadband communication section in the “poweron” state, much time can be spent in the sleep state.

Also, with a radio communication apparatus of the present invention, atone signal, which is a narrowband signal, is transmitted beforetransmitting a broadband signal that communicates a command or data, andtherefore only a narrowband signal reception wait state need be used. Itis therefore possible for a radio communication apparatus to keepstandby power consumption low compared with a case in which a broadbandsignal is constantly energized (power on).

Embodiment 2

A radio communication apparatus according to this embodiment transmits aprobe request, or returns a response, by means of a directional antennato all surrounding nodes. The configuration of a radio communicationapparatus according to this embodiment is identical to the configurationaccording to Embodiment 1, but the directional antenna communicationrange must be an area that allows all nodes of the probe request framecoverage area to communicate with each other. For example, when thedirectional antenna coverage area is an area of radius r, as shown inFIG. 17, a state is established in which arbitrary nodes B and C withina circle of radius r/2 and with its center at a point r/2 in thedirection in which the antenna is facing can perform mutual transmissionand reception. When a radio communication apparatus in such anarrangement issues a probe request, a response thereto can achievecollision avoidance by means of normal carrier sensing.

A radio communication apparatus according to this embodiment is moresuited to an access point whose orientation is fixed than to a mobilecommunication terminal whose orientation changes.

Probe request and response operations of radio communication apparatusesconfigured in this way will now be described.

Probe request/response operations according to this embodiment differfrom Embodiment 1 in that, after a probe request node has transmittedbeginning tone 1 to all neighbor nodes, it makes probe requests on asector-by-sector basis.

First, a probe request node transmits beginning tone 1 in the same wayas with an ordinary probe. On the other hand, a responding nodetransmits beginning tone 2. Then the probe request node declares thatthis is a sector probe, and reports that a probe request has started.Next, the probe request node transmits only a send/receive tone withdirectivity narrowed down to each sector. A peripheral responding nodethat receives such a send/receive tone with no data starts a back-offcounter and returns its response randomly. The probe request nodemeasures the maximum back-off time assigned to each sector, and aftersearching all sectors, transmits beginning tone 1 again and thentransmits “probe end”.

As described above, according to the present invention a sector probenarrows down the range in which transmission is performed compared withan ordinary probe, enabling the possibility of a collision to beeliminated by means of carrier sensing alone. Also, since thecommunication range is narrow, a maximum back-off count and the like canbe limited, resulting in the possibility of probe responses convergingat high speed.

As with an ordinary probe request, only one sector probe is executed ina probe slot, but a silent node may also receive a plurality ofbeginning tones 2. In this case, the silent node cannot return to thenormal standby state unless beginning tone 2, which is to be receivedbefore “probe end” is transmitted, is received the number of timesbeginning tone 2 is received. If two beginning tones 2 are not receivedfor some reason, the silent node remains silent during the maximumback-off count.

Embodiment 3

A radio communication method according to this embodiment uses asend/receive tone and end tone in the same way as in Embodiment 1, butdiffers in not using beginning tones 1 and 2.

FIG. 18 is a timing chart explaining the super-frame tone signals andframe according to this embodiment.

In FIG. 18, a super-frame 1501 is composed of end tone slots 1502 and atransmission/reception period 1503. There are only two tone signals—anend tone 1511 and a send/receive tone 1513- and a send/receive tone 1512transmitted in an end tone re-synchronization slot 1504, which is aspecial time period after an end tone is transmitted, is given a specialdesignation of “probe tone”.

A send/receive tone, when received by transmission/reception period1503, gives notification of transmission/reception of a command or dataframe by means of a broadband signal in the same way as in Embodiment 1.However, send/receive tone 1512 received after end tone reception in anend tone slot gives notification that a broadband signal reception waitstate is to be set and an RTS/CTS-e control frame is to be acquired inthe next super-frame. Then the radio communication apparatus transmits aprobe response at random timing in the next super-frame in which acontrol frame is acquired.

End tone processing is the same as in Embodiment 1.

FIG. 19 is a configuration diagram showing the configuration of a radiocommunication apparatus according to this embodiment. The configurationin this embodiment differs from that of Embodiment 1 shown in FIG. 2 inhaving a probe tone control section 161 instead of beginning tonecontrol section 134.

On receiving a probe tone signal from another radio communicationapparatus, probe tone control section 161 directs frametransmitting/receiving section 131 to perform RTS/CTS-e frame receptionin that super-frame.

Also, when probe transmitting section 137 receives an inquiry concerningthe surrounding situation from upper layer processing section 104, probetone control section 161 is directed to transmit a probe tone from probetransmitting section 137. Then probe tone control section 161 causesnarrowband communication section 102 to transmit a send/receivetone—that is, a probe tone—after the end tone.

Operations whereby radio communication apparatuses having the aboveconfiguration make a probe request and a response thereto will now bedescribed.

FIG. 20A is an operation flowchart of a probe-request-source radiocommunication apparatus according to Embodiment 3 of the presentinvention, and FIG. 20B is an operation flowchart of a probe-respondingradio communication apparatus.

In FIG. 20A, first, when probe transmitting section 137 receives aninquiry concerning the surrounding situation from upper layer processingsection 104, it recognizes probe request generation (step S1701), anddirects probe tone control section 161 to transmit a probe tone. Probetone control section 161 receives this and, after end tone transmission(step S1702), transmits send/receive tone 1512—that is, a probe tone—vianarrowband communication section 102 (step S1703).

Following this, after time management section 132 transmits an end tone,broadband communication section 101 is turned on, a probe response framereception wait state is entered (step S1704). Then, when broadbandcommunication section 101 receives a probe response frame, frametransmitting/receiving section 131 stores and updates acquiredtransmitting radio communication apparatus information such asattributes and communication environment (step S1705).

Next, if the communicating party matches the attributes of thisapparatus, RTS/CTS-e data frame transmitting section 135 transmits timereservation information until the start of RTS-e command and datatransmission in order to start transmission/reception (step S1706).

Following this, when the reserved time has elapsed (step S1707),RTS/CTS-e data frame transmitting section 135 transmits a data frame(step S1708). In steps S1705 through S1708, processing is performed inparallel by receiving probe requests from a plurality of radiocommunication apparatuses.

On the other hand, in FIG. 20B, when a radio communication apparatusreceives a probe tone (step S1720) it becomes a responding node, andturns on broadband communication section 101 (step S1721). Thenbroadband communication section 101 enters a broadband signal receptionwait state during that super-frame, and receives an RTS/CTS-e frametransmitted by another radio communication apparatus (step S1722).

Then, when time management section 132 receives an end tone (step S1723)and the next super-frame begins, probe receiving section 136 generatesattribute, communication environment, and suchlike information formaking a probe response, and gives a directive for probe responsetransmission to frame transmitting/receiving section 131. Frametransmitting/receiving section 131 starts a back-off count in thetransmission/reception period, and transmits a probe response frame inan empty slot (step S1724).

Thus, according to the present invention, since a probe response nodecompletes reception during one super-frame, which is the maximum timefor which RTS/CTS-e reception can be reserved by RTS/CTS-e, a proberequest node and probe response node can start RTS/CTS-e sequenceimmediately. Also, in a radio communication method according to thisembodiment, since a probe slot is not provided, that time can also beused for data transmission/reception. Furthermore, since a beginningtone is not used, it is also possible to shorten an end tone.

In this embodiment, individual tones in tone signals have beenidentified by differences in duration, but this is not a limitation, andthe same kind of effect can also be achieved by means of differences infrequency, relative magnitudes of field strength, temporal fluctuationsin field strength, intermittent signal patterns, and so forth.

Embodiment 4

A radio communication apparatus according to this embodiment is a mobilefile exchange apparatus incorporating a MAC protocol that implements theradio communication method of Embodiment 3. Exchanged files are musicfiles, video files, and game software.

FIG. 21 is a configuration diagram of a mobile file exchange apparatusaccording to this embodiment.

In FIG. 21, a mobile file exchange apparatus has a touch-panel display1801, a voice terminal 1802, an image input/output command receivingsection 1803, a voice input/output voice codec 1804, a main CPU 1805, ahard disk apparatus 1806, MAC interface memory 1807, an external mediasection 1808, a broadband communication section 101, a narrowbandcommunication section 102, a MAC control section 103, and an antenna105.

Broadband communication section 101, narrowband communication section102, MAC control section 103, and antenna 105 are identical to thosedescribed in Embodiment 2.

The operation of this mobile file exchange apparatus will now bedescribed.

First, music software, video software, and game software playbackoperations will be described.

First, a user installs the software he wishes to use from external mediasection 1808, and stores it in hard disk apparatus 1806. Then a commandinput from touch-panel display 1801 is converted to a plurality ofsignals by image input/output command receiving section 1803, and thenconveyed to main CPU 1805.

When a music playback command is input, main CPU 1805 gives a directiveto voice input/output voice codec 1804, which decodes music softwarefrom hard disk apparatus 1806 and outputs it from voice terminal 1802.

When a command that executes video or a game is input, in addition tovoice playback, main CPU 1805 displays video on touch-panel display 1801via image input/output command receiving section 1803.

Next, an operation whereby music software, video software, or gamesoftware file exchange is performed with another mobile file exchangeapparatus will be described.

First, in order to start a millimeter wave UWB (broadband signal)communication procedure when beginning file exchange, on receiving astart command from main CPU 1805, MAC control section 103 causesnarrowband communication section 102 to search for an end tone. Then,when narrowband communication section 102 detects an end tone,re-synchronization processing is started that performs synchronizationwith the first end tone detected.

Next, when MAC control section 103 receives a probe tone, narrowbandcommunication section 102 enters an RTS/CTS-e control frame receptionwait state in order to transmit a probe response. Then broadbandcommunication section 101 transmits a response randomly in thesuper-frame one super-frame later.

Then narrowband communication section 102 transmits an end tone for endtone re-synchronization once in N times. Count N depends on thesuper-frame period time, but a count that gives a 1-to-2-second periodis suitable. Counting is performed from the time of joining in the caseof anode that newly joins a super-frame group, and from execution of theprevious super-frame group re-synchronization processing in the case ofother nodes. These nodes enter an end tone reception wait state duringre-synchronization processing, and are synchronized at the timing atwhich a new end tone is received.

If a probe tone has not been transmitted and received even once within apredetermined number of end tones, or in the case of addition to a newsuper-frame group through end tone re-synchronization processing, eachnode transmits a probe tone. Each node that receives a probe tonereceives an RTS/CTS-e frame while continuing to performre-synchronization processing. Then, after waiting for reception of onesuper-frame, each node that has received a probe tone transmits a proberesponse after the elapse of a random time period. Probe responsetransmission by each node is performed during the next super-frame aftertransmission of the probe tone.

Next, the probe request node checks the attribute list of nodes forwhich there was a response, and for those that returned music softwareexchange, video exchange, and game software exchange attributes,performs differential exchange—that is, exchanges only softwarepossessed by one and not possessed by the others. Therefore, a node thathas started exchange first transmits a list of IDs of its ownexchangeable software. Then a node for which exchange has been presentedtransmits a list of IDs of its own exchangeable software in response tothe received list, and also issues a transfer request for softwarepossessed by the counterpart node that it does not possess itself andhas no experience of exchanging for several months.

A node that has initiated a file exchange request responds to a softwaretransfer based thereupon and also makes its own transfer request to theresponding side. In file exchange processing, transfer operations of afile of a mutually predetermined volume—for example, 50 MB—at a time arerepeated, and are continued until the counterpart node is no longer aneighboring node or transfer ends. Then, if necessary, the requestingnode updates the transfer time by re-exchange of an RTS/CTS-e frame.

FIG. 22 shows a music software file list managed by a mobile fileexchange apparatus.

In FIG. 22, each music ID is identified by a TOC (Table of Content) 1901and a track number 1904. A title 1902 and artist name 1903 are input bya user or input by means of a CDDB (CD number database) via an accesspoint. These are user information items and are not directly related tofile exchange operations.

A music file acquired from a CD, the Internet, or the like, is copied tohard disk apparatus 1806 by external media section 1808. At this time, amedia flag 1905 is “on”, a shadow flag 1906 is “off”, and a time limit1907 is “unlimited”. A list transmitted at the time of media exchangewith another mobile file exchange apparatus has only software with mediaflag 1905 “on”. Exchanged software also remains in its own file list asa song with media flag 1905 in the “on” state, but a time limit is set.For example, when the shadowing time limit is set as 100 days, an itemthat has not been played back even once after the elapse of 100 days ismade a shadow file. Here, a shadow file means a file whose existence canbe recognized by a user, but that cannot be played back. However, sincemedia flag 1905 is “on” and a music file actually exists in hard diskapparatus 1806, it can be treated as one of one's own exchange files.

When the shadowing time limit is exceeded or the possible number ofplayback times is reached, a file is made a shadow file, and a new timelimit is set. Then 100 days is newly set with this as a deletion limit.When this period is exceeded, music file software is deleted from harddisk apparatus 1806. At this time, an entry with media flag 1905 “off”and the shadow flag “on” is left in the file list with a re-entrysuppression time limit set. This re-entry suppression time limitrestricts the making of an entry again for a file for which there is nomusic file already but for which test-listening has been carried outonce, which enables a state in which the same file can be listened toany number of times to be prevented. When a re-entry suppression timelimit is exceeded, the entry itself disappears, and re-entry becomespossible.

it is also possible to select only items more to one's taste among alarge number of exchanged files by, for example, specifying a genre, orrestricting music file formats to be opened. A file not to one's tasteis made a shadow file immediately and deleted if the time limit isreached without its having been viewed by the user.

When the user copies that media to another device from external mediasection 1808, main CPU 1805 confirms that the media flag is “on” andthen moves the millimeter wave UWB access point and searches.Alternatively, the user connects to an IP network from a mobile phonewith relay capability by means of millimeter wave UWB, confirms thatauthentication and charging have been carried out using electroniccommerce, and then creates an entry with an unlimited time limit in thefile list. Then main CPU 1805 sets shadow flag 1906 to “off” and copiesa software file in the hard disk apparatus to an external media. Wheninstalling purchased software from an external media to one's own mobilefile exchange apparatus, also, charging is not necessary butauthentication is. This is because the exchange of software whosecirculation is not desired becomes possible.

Also, when relaying to an IP network by means of millimeter wave UWB, itis desirable for IP processing to terminate at an access point or mobilephone. If this is not done, although an IP address is assigned,millimeter wave UWB will cause confusion in mobile communications with aprivate address implemented by ordinary IPv4.

However, since using a network address for each access point results ininefficient address assignment, it is preferable to use IPv6 or toemploy a configuration whereby TCP/IP or higher data is exchanged on amillimeter wave UWB link.

In the above implementation example, the description of exchanged fileshas been limited to music files, but video file and game software fileexchange can also be managed in a similar way.

Also, when exchanging a list of software, if information indicating thatthe file list time limit is unlimited (that is, that the software hasbeen purchased) is also exchanged, peripheral users can create rankingsof purchased software. This can be a purchasing aid for users. Commentssuch as software recommendations may also be included in the rankinglist.

Furthermore, if a mobile file exchange apparatus performs file receptionof the mobile file exchange apparatus's own control software, it ispossible for updating to be carried out automatically. In this case, itis desirable to enable file exchange to be performed on a priority basisby adding a flag indicating priority or the like to the file.

Embodiment 5

FIG. 23 is a configuration diagram of a mobile file exchange apparatusaccording to this embodiment. The configuration in this embodimentdiffers from that of a mobile file exchange apparatus according toEmbodiment 4 in also having a unidirectional directional antenna 2001.

This antenna 2001 is used when it is wished to perform file exchangewhile visually identifying an opposite party with whom the user wants tocommunicate.

FIG. 24 is a sequence diagram for connecting a mobile file exchangeapparatus to an access point.

When a probe request command for an access point 2101 is input from thetouch panel of a mobile file exchange apparatus 2102, mobile fileexchange apparatus 2102 transmits a probe tone at its own end tonetiming. If another mobile file exchange apparatus 2103 transmits an endtone at this time, mobile file exchange apparatus 2102 re-synchronizeswith this and transmits a probe tone again.

Next, mobile file exchange apparatus 2101 awakened from sleep by theprobe tone transmits a probe response.

Then mobile file exchange apparatus 2102 displays access point 2101attribute information and so forth transmitted in this probe response ontouch-panel display 1801. For example, “Access point—music fileexchange” may be displayed.

Next, when the user selects that access point, the display on thetouch-panel display is subsequently updated by data exchange usingInternet hypertext (http) or the like, and, for example, “Connect” orsuchlike command input is performed. At this time, music softwarecharging is performed, for example.

As described above, according to a mobile file exchange apparatus ofthis embodiment, by means of a restriction of physically directing anantenna toward a target node, a requesting node can start communicationand erroneous specification of a counterpart node can be prevented.

Also, if a plurality of mobile file exchange apparatuses are present ina specified direction, and there are a plurality of responses,differences in the directions of arrival of each probe responseaccording to probe response direction-of-arrival estimation aredisplayed on a display as a plan view. By this means, the user caneasily decide which mobile file exchange apparatus to select from amongmany probe responses.

Embodiment 6

A configuration according to Embodiment 6 will now be described withreference to FIG. 25. FIG. 25 is a block diagram showing theconfiguration of a signal communication section 2500 of a radiocommunication apparatus according to this embodiment.

A radio communication apparatus according to this embodiment differsfrom that of Embodiment 1 in having a configuration in which the partscomprising broadband communication section 101 and narrowbandcommunication section 102 are not separated into two independent blocks,but instead a signal communication section 2500 is provided that is oneintegrated block. The configuration and operation of this embodimentcorresponding to MAC control section 103 and other parts other thanbroadband communication section 101 and narrowband communication section102 in Embodiment 1 are identical to those of Embodiment 1, andtherefore a description thereof is omitted here.

Signal communication section 2500 is composed of a tone signalcommunication section 2510, a data signal communication section 2520,and a carrier signal source 2502. Tone signal communication section 2510is equipped with a transmit/receive switch 2514, a frequency converter2516, a frequency converter 2518, and a tone signal control section2519. Similarly, data signal communication section 2520 is equipped witha filter 2522, a transmit/receive switch 2524, a demodulator 2526, amodulator 2528, and a data signal control section 2529.

When transmitting, tone signal communication section 2510 generates atone signal of predetermined length from a tone signal control signalinput from MAC control section 103, performs frequency conversion onthis tone signal, and outputs it to a duplexer 2530. Here, “tone signalcontrol signal” does not mean an actual tone signal of predeterminedlength as in FIG. 4, but a logical tone signal indicating what tonesignal a signal is, so to speak. In Embodiments 1 through 5, there maysimply be a tone signal. Tone signal communication section 2510 performsfrequency conversion of the tone signal input from duplexer 2530 toconvert it to a tone signal control signal, and outputs this to MACcontrol section 103.

“Tone signal” means a “tone signal control signal” that controlsbaseband tone signal generation, a “tone signal” for which amplitude,phase, or suchlike modulation is not performed, or a “tone signalsuperimposed on a carrier” generated by multiplying a tone signalcarrier by a carrier frequency.

When transmitting, a filter 2512 band-limits a tone signal input fromtransmit/receive switch 2514 to a predetermined frequency, and outputsthe signal to duplexer 2530. When receiving, filter 2512 band-limits atone signal input from duplexer 2530 to a predetermined frequency, andoutputs the signal to transmit/receive switch 2514.

Transmit/receive switch 2514 performs signal connection and directionswitching between transmission and reception so that, when transmitting,a post-frequency-conversion tone signal input from frequency converter2518 is output to filter 2512, and when receiving, a tone signal inputfrom filter 2512 is output to frequency converter 2516.

Frequency converter 2516 performs frequency conversion of a tone signalinput from transmit/receive switch 2514. That is to say, frequencyconverter 2516 converts a tone signal to a baseband signal based on acarrier output from carrier signal source 2502, and outputs theconverted signal to tone signal control section 2519.

When transmitting, frequency converter 2518 performs frequencyconversion of a tone signal input from tone signal control section2519—that is, converts it to a signal with the carrier output fromcarrier signal source 2502 as the center frequency—and outputs theconverted signal to transmit/receive switch 2514.

When transmitting, tone signal control section 2519 generates a tonesignal based on a unique data pattern held in tone signal controlsection 2519 in accordance with a tone signal control signal input fromMAC control section 103, and outputs this signal to frequency converter2518. When receiving, tone signal control section 2519 has a tone signalinput from frequency converter 2516 as input, determines the type oftone signal according to the length of the tone signal, generates acorresponding tone signal control signal, and outputs this signal to MACcontrol section 103.

Similarly, when transmitting, data signal communication section 2520modulates a data signal input from MAC control section 103 and outputsthe modulated signal to duplexer 2530. When receiving, data signalcommunication section 2520 performs frequency conversion of a datasignal input from duplexer 2530, and outputs the resulting signal to MACcontrol section 103.

When transmitting, filter 2522 band-limits a data signal input fromtransmit/receive switch 2524 to a predetermined frequency, and outputsthe signal to duplexer 2530. When receiving, filter 2522 band-limits adata signal input from duplexer 2530 to a predetermined frequency, andoutputs the signal to transmit/receive switch 2524.

Transmit/receive switch 2524 performs signal connection and directionswitching between transmission and reception so that, when transmitting,a post-modulation data signal input from modulator 2528 is output tofilter 2522, and when receiving, a data signal input from filter 2522 isoutput to demodulator 2526.

Demodulator 2526 performs demodulation of a data signal input fromtransmit/receive switch 2524. That is to say, demodulator 2526 convertsa data signal to a baseband signal based on a carrier output fromcarrier signal source 2502, and outputs the converted signal to datasignal control section 2529.

When transmitting, modulator 2528 modulates a data signal input fromdata signal control section 2529—that is, converts it to a signal withthe carrier output from carrier signal source 2502 as the centerfrequency—and outputs the modulated signal to transmit/receive switch2524.

When transmitting, data signal control section 2529 outputs a datasignal input from MAC control section 103 to modulator 2528. Whenreceiving, data signal control section 2529 outputs a data signal inputfrom demodulator 2526 to MAC control section 103.

Carrier signal source 2502 generates a carrier, and outputs the carrierto frequency converter 2516 and demodulator 2526. FIG. 25 shows aconfiguration in which tone signal communication section 2510 and datasignal communication section 2520 share carrier signal source 2502.

A configuration with separate carrier signal sources can also be used,both when signals with different center frequencies are used for a tonesignal and a data signal, and when signals with the same centerfrequency are used. In Embodiment 1, such a configuration is implementedwhen data signal communication section 2520 and a carrier signal sourceare used in broadband communication section 101, and tone signalcommunication section 2510 and a separate carrier signal source are usedin narrowband communication section 102. Even if there is a singlecarrier signal source, different center frequencies can be used for tonesignal communication section 2510 and data signal communication section2520 by changing the frequency from the carrier signal source 2502frequency using a mixer or suchlike frequency converting element. Withregard to the antenna, also, a configuration may be used in which aplurality of antennas are divided between tone signal use and datasignal use according to the signal band.

Although it is preferable to use a narrowband signal as a tone signaland to use a broadband signal as a data signal in this embodiment, thepresent invention is not limited to this, and it is possible to set tonesignal and data signal bands without regard to relative band size.

It also goes without saying that the present invention also includes aconfiguration in which a narrowband communication section and broadbandcommunication section of Embodiments 2 through 5 are replaced by tonesignal communication section 2510, data signal communication section2520, and carrier signal source 2502 of this embodiment.

The operation of signal communication section 2500 of a radiocommunication apparatus of Embodiment 6 will now be described.

First, the operation of tone signal communication section 2510 will bedescribed. When transmitting, tone signal control section 2519 generatesa tone signal based on a unique data pattern held in tone signal controlsection 2519 in accordance with a tone signal control signal input fromMAC control section 103, and outputs this signal to frequency converter2518.

Then frequency converter 2518 performs frequency conversion of the tonesignal input from tone signal control section 2519—that is, converts itto a signal with the carrier output from carrier signal source 2502 asthe center frequency—and outputs the frequency-converted signal totransmit/receive switch 2514.

Next, transmit/receive switch 2514 outputs the post-frequency-conversiontone signal input from frequency converter 2518 to filter 2512. Thenfilter 2512 band-limits the tone signal input from transmit/receiveswitch 2514 to a predetermined frequency, and outputs the band-limitedtone signal to duplexer 2530.

On the other hand, when receiving, filter 2512 band-limits a tone signalinput from duplexer 2530 to a predetermined frequency, and outputs theband-limited tone signal to transmit/receive switch 2514.

Transmit/receive switch 2514 outputs the tone signal input from filter2512 to frequency converter 2516. Frequency converter 2516 performsfrequency conversion of the tone signal input from transmit/receiveswitch 2514. That is to say, frequency converter 2516 converts the tonesignal to a baseband signal based on a carrier output from carriersignal source 2502, and outputs the converted signal to tone signalcontrol section 2519.

Tone signal control section 2519 has the tone signal input fromfrequency converter 2516 as input, determines the type of tone signalaccording to the length of the tone signal, generates a correspondingtone signal control signal, and outputs the generated tone signalcontrol signal to MAC control section 103.

Next, the operation of data signal communication section 2520 will bedescribed.

When data signal communication section 2520 is transmitting, data signalcontrol section 2529 outputs a data signal input from MAC controlsection 103 to modulator 2528.

Modulator 2528 modulates a data signal input from data signal controlsection 2529—that is, converts it to a signal with the carrier outputfrom carrier signal source 2502 as the center frequency—and outputs themodulated data signal to transmit/receive switch 2524.

Next, transmit/receive switch 2524 outputs the post-modulation datasignal input from modulator 2528 to filter 2522. Then filter 2522band-limits the data signal input from transmit/receive switch 2524 to apredetermined frequency, and outputs the band-limited data signal toduplexer 2530.

On the other hand, when receiving, filter 2522 band-limits a data signalinput from duplexer 2530 to a predetermined frequency, and outputs theband-limited data signal to transmit/receive switch 2524.

Transmit/receive switch 2524 outputs the data signal input from filter2522 to demodulator 2526.

Demodulator 2526 performs demodulation of the data signal input fromtransmit/receive switch 2524. That is to say, demodulator 2526 convertsthe data signal to a baseband signal based on a carrier output fromcarrier signal source 2502, and outputs the converted signal to datasignal control section 2529.

Data signal control section 2529 outputs the data signal input fromdemodulator 2526 to MAC control section 103.

Thus, in this embodiment, a configuration is employed in which tonesignal communication section 2510 and data signal communication section2520 share carrier signal source 2502, enabling a low-cost radiocommunication apparatus with a small number of parts to be provided.

Embodiment 7

The configuration and operation of a radio communication apparatusaccording to Embodiment 7 will now be described.

FIG. 25 of Embodiment 6 shows an example in which tone signalcommunication section 2510 and data signal communication section 2520are provided as two transmission systems in order to transmit abroadband signal and a tone signal simultaneously. However, ifsimultaneous transmission is not performed, a single transmission systemis sufficient, and therefore a radio communication apparatus with such aconfiguration is presented here as Embodiment 7, and its configurationand operation are described below.

The configuration of Embodiment 7 will now be described with referenceto FIG. 26. FIG. 26 is a block diagram showing the configuration of asignal communication section 2600 of a radio communication apparatusaccording to this embodiment.

The configuration and operation of this embodiment corresponding to MACcontrol section 103 and other parts other than broadband communicationsection 101 and narrowband communication section 102 in Embodiment 1 areidentical to those of Embodiment 1, and therefore a description thereofis omitted here.

Signal communication section 2600 is composed of a communication section2610 and a carrier signal source 2502. Communication section 2610 isequipped with a filter 2612, a transmit/receive switch 2614, ademodulator 2616, a modulator 2618, and a signal control section 2619.

When transmitting a tone signal, communication section 2610 generates atone signal from a tone signal control signal input from MAC controlsection 103, and outputs this tone signal to modulator 2618. Whenreceiving a tone signal, communication section 2610 has a tone signalinput from demodulator 2616 as input, determines the type of tone signalaccording to the length of the tone signal, generates a correspondingtone signal control signal, and outputs this signal to MAC controlsection 103.

When transmitting a data signal, communication section 2610 modulates adata signal input from MAC control section 103 and outputs the modulatedsignal to directivity control section 106. When receiving a data signal,communication section 2610 demodulates a data signal input fromdirectivity control section 106, and outputs the demodulated signal toMAC control section 103.

When transmitting, filter 2612 band-limits a tone signal or data signalinput from transmit/receive switch 2614 to a predetermined frequency,and outputs the signal to directivity control section 106. Whenreceiving, filter 2612 band-limits a tone signal or data signal inputfrom directivity control section 106 to a predetermined frequency, andoutputs the signal to transmit/receive switch 2614.

Transmit/receive switch 2614 performs signal connection and directionswitching between transmission and reception so that, when transmitting,a post-frequency-conversion or post-modulation tone signal or datasignal input from modulator 2618 is output to filter 2612, and whenreceiving, a tone signal or data signal input from filter 2612 is outputto demodulator 2616.

Demodulator 2616 performs frequency conversion or demodulation of a tonesignal or data signal input from transmit/receive switch 2614. That isto say, demodulator 2616 converts a tone signal or data signal to abaseband signal based on a carrier output from carrier signal source2502, and outputs the converted signal to signal control section 2619.

When transmitting, modulator 2618 performs frequency conversion ormodulation of a tone signal or data signal input from signal controlsection 2619—that is, converts it to a signal with the carrier outputfrom carrier signal source 2502 as the center frequency—and outputs theresulting signal to transmit/receive switch 2614.

When transmitting a tone signal, signal control section 2619 outputs atone signal to modulator 2618 based on a unique data pattern held insignal control section 2619 in accordance with a tone signal controlsignal input from MAC control section 103. When transmitting data,signal control section 2619 outputs a data signal input from MAC controlsection 103 to modulator 2618.

When receiving a tone signal, signal control section 2619 has a tonesignal input from demodulator 2616 as input, determines the type of tonesignal according to the length of the tone signal, generates acorresponding tone signal control signal, and outputs this signal to MACcontrol section 103. When receiving a data signal, signal controlsection 2619 has a data signal input from demodulator 2616 as input, andoutputs this signal to MAC control section 103.

The operation of a radio communication apparatus according to Embodiment7 will now be described.

When transmitting a tone signal, signal control section 2619 outputs atone signal to modulator 2618 based on a unique data pattern held insignal control section 2619 in accordance with a tone signal controlsignal input from MAC control section 103. When transmitting a datasignal, signal control section 2619 outputs a data signal input from MACcontrol section 103 to modulator 2618.

Then modulator 2618 performs frequency conversion or modulation of atone signal or data signal input from signal control section 2619—thatis, converts it to a signal with the carrier output from carrier signalsource 2502 as the center frequency—and outputs a modulator outputsignal 2702 to transmit/receive switch 2614.

Next, transmit/receive switch 2614 outputs a post-frequency-conversionor post-modulation tone signal or data signal (modulator output signal2702) input from modulator 2618 to filter 2612. Filter 2612 band-limitsthe tone signal or data signal input from transmit/receive switch 2614to a predetermined frequency, and outputs the band-limited signal todirectivity control section 106.

On the other hand, when receiving, filter 2612 band-limits a tone signalor data signal input from directivity control section 106 to apredetermined frequency, and outputs the band-limited signal totransmit/receive switch 2614.

Transmit/receive switch 2614 outputs the tone signal or data signalinput from filter 2612 to demodulator 2616. Demodulator 2616 performsfrequency conversion or demodulation of the tone signal or data signalinput from transmit/receive switch 2614. That is to say, demodulator2616 converts the tone signal or data signal to a baseband signal basedon a carrier output from carrier signal source 2502, and outputs theconverted signal to signal control section 2619.

When receiving a tone signal, signal control section 2619 has a tonesignal input from demodulator 2616 as input, determines the type of tonesignal according to the length of the tone signal, generates acorresponding tone signal control signal, and outputs this signal to MACcontrol section 103. When receiving a data signal, signal controlsection 2619 outputs a data signal input from demodulator 2616 to MACcontrol section 103.

FIG. 27 shows an example of the signal waveform of modulator outputsignal 2702 after an input modulator input signal 2701 has undergonemodulation or frequency conversion by modulator 2618 in this case. Inthe signals input to modulator 2618, signal width 2711 of a tone signal2710 and signal width 2721 of a data signal 2720 differ, and a modulatoroutput signal containing a sine wave component also differs in widthaccording to this signal width. It goes without saying that a signalwith a wide width is a narrowband signal, and a signal with a narrowwidth is a broadband signal. Examples of signal widths are 1 μsec fortone signal 2710 and 1 nsec for data signal 2720, but the signal widthsare not limited to these, and will vary greatly depending on theapplication system. Also, a tone signal need not necessarily be anarrowband signal, and tone signal width 2711 may be equal to or smallerthan data signal width 2721.

Also, with regard to the method of separating a tone signal and datasignal when receiving, if a tone signal and data signal are of differentfrequencies, for example, it is possible to separate the two by filterband. Similarly, if tone signal and data signal are not transmittedsimultaneously, it is possible to separate them temporally. Furthermore,if they are transmitted at the same frequency and the same time, it ispossible to separate them by changing the transmit signal power. In thiscase, separation can be performed by means of received power thresholdvalue in a demodulator 2616 by, for example, making the amplitudesmaller and making the transmission power smaller for a tone signalhaving a long signal time, and making the amplitude larger and makingthe transmission power larger for a data signal.

Thus, in this embodiment, a configuration is employed in which a tonesignal and a data signal are processed by a single signal communicationsection, as a result of which the configuration is simple and the numberof parts small, and a low-cost, low-power-consumption radiocommunication apparatus can be provided.

A radio communication method of the present invention is a radiocommunication method whereby a plurality of radio communicationapparatuses communicate with each other in an ad hoc network, and has astep of transmitting an end tone for identifying the end of asuper-frame from one radio communication apparatus, and a step ofsynchronizing at another radio communication apparatus, the end of itsown super-frame when having received that end tone.

By this means, a radio communication apparatus performs synchronizationwith a super-frame by using a low-power-consumption tone signal, withoutusing a beacon provided by a modulated signal, enabling powerconsumption to be reduced as compared with a conventional method.

Also, a radio communication method of the present invention further hasa step of transmitting a send/receive tone for giving notification ofdata transmission from the one radio communication apparatus whileperforming carrier sensing after the elapse of a predetermined time fromthe end of a super-frame, and a step of transmitting a data signal aftercompletion of transmission of that send/receive tone.

By this means, a radio communication apparatus can detect the start ofdata reception by monitoring only a tone signal, making it possible tokeep standby power consumption low.

Also, a radio communication method of the present invention further hasa step of enabling reception of the data signal and receiving a datasignal at the one radio communication apparatus after receiving asend/receive tone from another radio communication apparatus, and a stepof transmitting the send/receive tone from the one radio communicationapparatus while performing carrier sensing when having received thatdata signal normally.

By this means, a radio communication apparatus need not wait forreception of a UWB or suchlike data signal, enabling standby powerconsumption to be reduced.

Also, in a radio communication method of the present invention, the stepof transmitting an end tone is a step of transmitting a narrowbandsignal end tone for identifying the end of a super-frame from the oneradio communication apparatus.

By this means, a radio communication apparatus performs synchronizationwith a super-frame by using a low-power-consumption, narrowband tonesignal, without using a beacon provided by a modulated signal, enablingpower consumption to be reduced as compared with a conventional method.

Also, a radio communication method of the present invention further hasa step of transmitting a narrowband signal send/receive tone from theone radio communication apparatus while performing carrier sensing afterthe elapse of a predetermined time from the end of a super-frame, and astep of transmitting a broadband data signal from the one radiocommunication apparatus after completion of transmission of thesend/receive tone.

By this means, a radio communication apparatus can detect the start ofdata reception by monitoring only a narrowband signal, making itpossible to keep standby power consumption low.

Also, a radio communication method of the present invention further hasa step of enabling reception of a broadband signal and receiving thedata signal at the one radio communication apparatus after receiving asend/receive tone from another radio communication apparatus, and a stepof transmitting the narrowband send/receive tone from the one radiocommunication apparatus while performing carrier sensing when havingreceived the data signal normally.

By this means, a radio communication apparatus need not wait forreception of wideband signal such as a UWB, enabling standby powerconsumption to be reduced.

In a radio communication method of the present invention, an end tone istransmitted in an end tone slot set before and after the end of asuper-frame, and the one radio communication apparatus re-sets the endof a super-frame based on the end tone received first in an end toneslot.

By this means, it is possible for each radio communication apparatus ofa super-frame group to synchronize with the earliest end tone in asuper-frame.

Also, a radio communication method of the present invention has a stepof, when an end tone received from another radio communication apparatusis the first in an end tone slot, and reception is completed before thestart of transmission of its own end tone, re-setting the end of asuper-frame at that time of completion, at the one radio communicationapparatus, and a step of transmitting from the one radio communicationapparatus, its own end tone at the timing at which an end tone isreceived.

By this means, the time difference between an end tone received firstand the apparatus's own end tone can be kept smaller, making it possibleto synchronize with the same super-frame in a short time overall.

Also, a radio communication method of the present invention has a stepof, when there is a mixed plurality of super-frame groups that aregroups of radio communication apparatuses sharing a super-frame, a radiocommunication apparatus of a first super-frame group notifying anotherradio communication apparatus of its own super-frame group ofsynchronizing with a second super-frame, and that radio communicationapparatus of the first super-frame group waits for reception of an endtone from a second super-frame group across super-frames as a whole, andre-sets the end of the super-frame based on that received end tone.

By this means, it is possible for a radio communication apparatus tostart transmission/reception even if it encounters another super-framegroup in a mobile environment.

Also, in a radio communication method of the present invention, a radiocommunication apparatus belonging to a first super-frame group notifiesanother radio communication apparatus of synchronizing with asuper-frame of a second super-frame group by transmitting an end toneagain in an end tone slot after transmitting an end tone givingnotification of the current end, and another radio communicationapparatus belonging to the first super-frame group that receives thatend tone giving notification of that synchronizing transmits an end toneagain in an end tone slot after transmitting an end tone givingnotification of the current end.

By this means, a radio communication apparatus executesre-synchronization in super-frame group units, and all communicationsare possible since group convergence occurs without any fear of currentcommunication being disrupted.

Also, a radio communication method of the present invention provides ata narrowband tone signal, a beginning tone 1 and beginning tone 2defined by changing duration, and has a step of transmitting anarrowband signal beginning tone 1 for communication collision avoidancefrom a radio communication apparatus while performing carrier sensing, astep of transmitting a narrowband signal beginning tone 2 from a radiocommunication apparatus that receives that beginning tone 1, and a stepof stopping at a radio communication apparatus that receives thatbeginning tone 1 or beginning tone 2, transmitting a narrowband signalbeginning tone 1 from itself in the current super-frame.

By this means, when a plurality of responses are made in multicastcommunication or the like, each radio communication apparatus suppressestransmission so that responses are made one at a time.

Also, a radio communication method of the present invention has a stepof transmitting from a radio communication apparatus that transmitsbeginning tone 1, a probe request inquiring about attributes and/orcommunication environment by means of a broadband signal to a radiocommunication apparatus that transmits beginning tone 2, and a step oftransmitting from a radio communication apparatus that receives thatprobe request, a probe response containing information on its ownattributes and communication environment by means of a broadband signal.

By this means, a plurality of geographical reuses are possible for aradio communication apparatus in the same time period by causing proberequests to be performed by means of multicasting using a beginningtone.

A radio communication method of the present invention has a step oftransmitting a send/receive tone, from a radio communication apparatusthat receives a probe request, before transmitting a probe response, astep of transferring a received send/receive tone from a radiocommunication apparatus that transmits a probe request when havingreceived that send/receive tone, and a step of stopping at a radiocommunication apparatus that is not transmitting a probe request, thestart of transmission of a probe response from itself when havingreceived a send/receive tone.

By this means, contention between a request-side radio communicationapparatus and a response-side radio communication apparatus located nextto the neighboring radio communication apparatus of the request-sideradio communication apparatus can be kept to a minimum.

Also, a radio communication method of the present invention has a stepof counting by means of back-off a predetermined time until proberesponse reception is completed, at a radio communication apparatus thattransmits a probe request, and a step of transmitting a probe requestperiod end notification to a neighboring radio communication apparatusfrom a radio communication apparatus that transmits a probe request whenhaving finished counting the predetermined time.

By this means, a radio communication apparatus can terminate a probe inthe minimum necessary time.

Also, in a radio communication method of the present invention, in aprobe request a radio communication apparatus that transmits a proberequest configures a plurality of sectors by means of a plurality ofdirectional antennas, and when radio communication apparatuses in eachsector are in a state in which mutual transmission/reception ispossible, send/receive tone transmission performed by a radiocommunication apparatus that transmits a probe request is performed inorder on a sector-by-sector basis by each directional antenna.

By this means, it is possible for probe processing of a fixed radiocommunication apparatus to execute a probe operation efficiently bydeciding on a sector.

Also, a radio communication method of the present invention has a stepof counting by means of back-off a predetermined time until proberesponse reception is completed, at a radio communication apparatus thattransmits a probe request, and a step of transmitting a probe requestperiod end notification to a neighboring radio communication apparatusfrom a radio communication apparatus that transmits a probe request whenhaving finished a count of the predetermined time in all sectors.

By this means, a radio communication apparatus can make the sector waittime the minimum necessary.

Also, in a radio communication method of the present invention, whenhaving received a send/receive tone following an end tone in an end toneslot, the one radio communication apparatus acquires a control framecontaining data transmission/reception reservation informationtransmitted by a neighboring radio communication apparatus in thesuper-frame after the end of that end tone slot, and transmits a proberesponse containing its own attribute and communication environmentinformation and/or information on a time period reserved by a controlframe in a time period not reserved by a control frame of the nextsuper-frame.

By this means, a radio communication apparatus can perform timereservation of all sections of a data period by performing communicationusing RTS/CTS-e, enabling the entirety of a super-frame to be utilizedmore effectively than with a conventional method.

Also, the durations of narrowband signals (tone signals) used in a radiocommunication method of the present invention increase in send/receivetone, beginning tone 1, beginning tone 2, and end tone order, and an endtone is at least twice as long as beginning tone 2.

By this means, while a send/receive tone of a radio communicationapparatus must be as short as possible due to its relation tothroughput, an end tone can still be detected as an end tone even iftripled. Also, if two or more beginning tones 2 are emitted in the sameperiod, they will be regarded as beginning tones 2.

Also, a radio communication method of the present invention is a radiocommunication method of one radio communication apparatus whereby aplurality of radio communication apparatuses communicate with each otherin an ad hoc network, and has a step of measuring elapsed time in asuper-frame and transmitting an end tone for identifying the end, a stepof transmitting a send/receive tone for giving notification of datatransmission after the elapse of a predetermined time based on an endtime re-set based on the end tone transmitted first, and a step oftransmitting a data signal after completion of transmission of thatsend/receive tone.

Also, in a radio communication method of the present invention, the endtone and send/receive tone are narrowband signals, and the data signalis a broadband signal data signal.

Also, a radio communication method of the present invention has a stepof transmitting a narrowband signal beginning tone 1 for communicationcollision avoidance from the one radio communication apparatus whileperforming carrier sensing, and a step of receiving a beginning tone 2transmitted by another radio communication apparatus that receives thebeginning tone 1, at the one radio communication apparatus.

Also, a radio communication method of the present invention has a stepof transmitting from one radio communication apparatus that transmitsthe beginning tone 1, a probe request inquiring about attributes and/orcommunication environment by means of a broadband signal to the otherradio communication apparatus that transmits beginning tone 2, and astep of receiving a probe response containing information on its ownattributes and/or communication environment by means of a broadbandsignal from the other radio communication apparatus that receives theprobe request.

Also, a radio communication apparatus of the present invention has atone signal communication section that transmits and receives tonesignals, a data signal communication section that performs modulationand transmits and receives data by means of a broadband signal, a timemanagement section, and a frame transmitting/receiving section. Thistime management section measures elapsed time in a super-frame,transmits an end tone for identifying the end from the tone signalcommunication section, or receives an end tone via the tone signalcommunication section, and re-sets the end time based on the end tonereceived first before its own end time. The frame transmitting/receivingsection transmits a send/receive tone for giving notification of datatransmission from the tone signal communication section after the elapseof a predetermined time based on the end time re-set by the timemanagement section, and after transmission of that send/receive tone iscompleted, transmits data via the data signal communication section, orsets the data signal communication section to a reception-enabled statewhen a send/receive tone is received, and receives data from the datasignal communication section.

By means of this configuration, a radio communication apparatus canimplement super-frame synchronization between super-frame groups withoutusing a beacon.

Also, in a radio communication apparatus of the present invention, thetone signal communication section is a narrowband communication sectionthat transmits and receives narrowband tone signals, and the data signalcommunication section is a broadband communication section that performsmodulation and transmits and receives data by means of a broadbandsignal.

By means of this configuration, a radio communication apparatus canimplement super-frame synchronization between super-frame groups withoutusing a beacon.

A radio communication apparatus of the present invention also has are-synchronization control section. This re-synchronization controlsection gives notification of synchronizing with a super-frame ofanother group that does not share a super-frame to another radiocommunication apparatus belonging to the same group as itself thatshares a super-frame. Then an end tone of another group is monitored inall super-frame periods, and when that end tone is received, thesuper-frame end is re-set to, and an end tone is transmitted via thenarrowband communication section.

By this means, it is possible for a radio communication apparatus toperform synchronization with a super-frame of another super-frame group.

A radio communication apparatus of the present invention also has aprobe transmitting section that gives a directive for beginning tone 1transmission to a beginning tone control section, and upon subsequentnotification of reception of beginning tone 2 from that beginning tonecontrol section, gives a directive to the frame transmitting/receivingsection for transmission of a probe request frame requestingnotification of attribute and communication environment information toanother radio communication apparatus, and a probe receiving sectionthat, when having received the probe request, directs the frametransmitting/receiving section to transmit its own attribute and/orcommunication environment information.

By means of this configuration, a radio communication apparatus canimplement by means of a probe confirmation of the existence of a nodethat has been implemented by a beacon.

The present application is based on Japanese Patent Application No.2005-352992 filed on Dec. 7, 2005, the entire content of which isexpressly incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The present invention is useful for a radio communication method andradio communication apparatus in an ad hoc network, and is particularlysuitable for file exchange between radio communication apparatuses in amobility environment.

1. A radio communication method whereby a plurality of radiocommunication apparatuses communicate with each other in an ad hocnetwork, comprising: transmitting an end tone for identifying an end ofa super-frame from one radio communication apparatus; and synchronizingat another radio communication apparatus, an end of its own super-framewhen having received that end tone.
 2. The radio communication methodaccording to claim 1, further comprising: transmitting a send/receivetone for giving notification of data transmission from said one radiocommunication apparatus while performing carrier sensing after an elapseof a predetermined time from an end of a super-frame; and transmitting adata signal after completion of transmission of said send/receive tonefrom said one radio communication apparatus.
 3. The radio communicationmethod according to claim 2, further comprising: enabling reception ofsaid data signal and receiving said data signal at said one radiocommunication apparatus after receiving a send/receive tone from anotherradio communication apparatus; and transmitting said send/receive tonefrom said one radio communication apparatus while performing carriersensing when having received said data signal normally.
 4. The radiocommunication method according to claim 1, wherein an end tonetransmitted by said one radio communication apparatus is a narrowbandsignal.
 5. The radio communication method according to claim 2, whereina data signal transmitted by said one radio communication apparatus is abroadband data signal.
 6. The radio communication method according toclaim 5, further comprising: enabling reception of a broadband signaland receiving said data signal at said one radio communication apparatusafter receiving a send/receive tone from another radio communicationapparatus; and transmitting said narrowband send/receive tone from saidone radio communication apparatus while performing carrier sensing whenhaving received said data signal normally.
 7. The radio communicationmethod according to claim 4, wherein: said end tone is transmitted in anend tone slot set before and after an end of a super-frame; and said oneradio communication apparatus re-sets an end of a super-frame based onan end tone received first in an end tone slot.
 8. The radiocommunication method according to claim 7, further comprising: when anend tone received from another radio communication apparatus is thefirst in an end tone slot and reception is completed before a start oftransmission of its own end tone, re-setting an end of a super-frame oncompletion of reception of said end tone of said other radiocommunication apparatus, at said one radio communication apparatus; andtransmitting from said one radio communication apparatus, its own endtone at timing at which an end tone is received.
 9. The radiocommunication method according to claim 7 that, when there is a mixedplurality of super-frame groups that are groups of radio communicationapparatuses sharing said super-frame, further comprises: notifying atone radio communication apparatus belonging to a first super-framegroup, another radio communication apparatus belonging to said firstsuper-frame group of synchronizing with a second super-frame; andwaiting for reception of an end tone from a radio communicationapparatus belonging to said second super-frame group across super-framesas a whole, and re-setting an end of a super-frame based on a receivedend tone, at said one radio communication apparatus of said firstsuper-frame group.
 10. The radio communication method according to claim9, further comprising: notifying at said one radio communicationapparatus belonging to said first super-frame group, another radiocommunication apparatus belonging to said first super-frame group ofsynchronizing with a super-frame of said second super-frame group bytransmitting an end tone again in an end tone slot after transmitting anend tone giving notification of a current end; and transmitting an endtone again in an end tone slot from another radio communicationapparatus belonging to said first super-frame group that receives saidend tone giving notification of synchronizing after transmitting an endtone giving notification of a current end.
 11. The radio communicationmethod according to claim 5, further comprising: transmitting anarrowband signal beginning tone 1 for communication collision avoidancefrom said one radio communication apparatus while performing carriersensing; transmitting a narrowband signal beginning tone 2 from a radiocommunication apparatus that receives said beginning tone 1; andstopping at a radio communication apparatus that receives said beginningtone 1 or said beginning tone 2, transmitting a narrowband signalbeginning tone 1 from itself in a current super-frame.
 12. The radiocommunication method according to claim 11, further comprising:transmitting from a radio communication apparatus that transmits saidbeginning tone 1, a probe request inquiring about an attribute and/orcommunication environment by means of a broadband signal to a radiocommunication apparatus that transmits said beginning tone 2; andtransmitting from a radio communication apparatus that receives saidprobe request, a probe response containing information on its ownattribute and/or communication environment by means of a broadbandsignal.
 13. The radio communication method according to claim 12,further comprising: transmitting a send/receive tone from a radiocommunication apparatus that receives said probe request beforetransmitting said probe response; transferring a received send/receivetone from a radio communication apparatus that transmits said proberequest when having received said send/receive tone; and stopping at aradio communication apparatus that is not transmitting said proberequest, a start of transmission of said probe response from itself whenhaving received said send/receive tone.
 14. The radio communicationmethod according to claim 13, further comprising: counting by means ofback-off a predetermined time until reception of said probe response iscompleted, at a radio communication apparatus that transmits said proberequest; and transmitting a probe request period end notification to aneighboring radio communication apparatus from a radio communicationapparatus that transmits said probe request when having finishedcounting said predetermined time.
 15. The radio communication methodaccording to claim 13, wherein, in said probe request, a radiocommunication apparatus that transmits said probe request configures aplurality of sectors by means of a plurality of directional antennas,and when radio communication apparatuses in each sector are in a statein which mutual transmission/reception is possible, transmission of saidsend/receive tone performed by a radio communication apparatus thattransmits said probe request is performed in order on a sector-by-sectorbasis by each directional antenna.
 16. The radio communication methodaccording to claim 15, further comprising: counting by means of back-offa predetermined time until reception of said probe response iscompleted, at a radio communication apparatus that transmits said proberequest; and transmitting a probe request period end notification to aneighboring radio communication apparatus from a radio communicationapparatus that transmits said probe request when having finished a countof said predetermined time in all sectors.
 17. The radio communicationmethod according to claim 7, wherein said one radio communicationapparatus, when having received a send/receive tone following an endtone in an end tone slot, acquires a control frame containing datatransmission/reception reservation information transmitted by aneighboring radio communication apparatus in a super-frame after an endof that end tone slot, and transmits a probe response containing its ownattribute and communication environment information and/or informationon a time period reserved by said control frame in a time period notreserved by said control frame of a next super-frame.
 18. The radiocommunication method according to claim 11, wherein durations of saidnarrowband signals that are tone signals increase in send/receive tone,beginning tone 1, beginning tone 2, and end tone order, and beginningtone 2 is at least twice as long as beginning tone
 1. 19. A radiocommunication method of one radio communication apparatus whereby aplurality of radio communication apparatuses communicate with each otherin an ad hoc network, comprising: measuring elapsed time in asuper-frame and transmitting an end tone for identifying an end; a stepof transmitting a send/receive tone for giving notification of datatransmission after an elapse of a predetermined time based on an endtime re-set based on an end tone transmitted first; and transmitting adata signal after completion of transmission of that send/receive tone.20. The radio communication method according to claim 19, wherein: saidend tone and send/receive tone are narrowband signals; and said datasignal is a broadband signal.
 21. The radio communication methodaccording to claim 20, further comprising: transmitting a narrowbandsignal beginning tone 1 for communication collision avoidance from saidone radio communication apparatus while performing carrier sensing; andreceiving a beginning tone 2 transmitted by another radio communicationapparatus that receives said beginning tone 1 at said one radiocommunication apparatus.
 22. The radio communication method according toclaim 21, further comprising: transmitting a probe request inquiringabout an attribute and/or communication environment by means of abroadband signal from one radio communication apparatus that transmitssaid beginning tone 1 to said other radio communication apparatus thattransmits said beginning tone 2; and receiving a probe responsecontaining information on its own attribute and/or communicationenvironment by means of a broadband signal from said other radiocommunication apparatus that receives said probe request.
 23. A radiocommunication apparatus comprising: a tone signal communication sectionthat transmits and receives a tone signal; a data signal communicationsection that transmits and receives data; a time management section thatmeasures elapsed time in a super-frame, transmits an end tone foridentifying an end via said tone signal communication section, orreceives said end tone via said tone signal communication section, andre-sets an end time based on an end tone received first before its ownend time; and a frame transmitting/receiving section that transmits asend/receive tone for giving notification of data transmission from saidtone signal communication section after an elapse of a predeterminedtime based on an end time re-set by said time management section, andafter transmission of that send/receive tone is completed, transmitsdata via said data signal communication section, or sets said datasignal communication section to a reception-enabled state when havingreceived said send/receive tone, and receives data via said data signalcommunication section.
 24. The radio communication apparatus accordingto claim 23, wherein: said tone signal communication section is anarrowband communication section that transmits and receives anarrowband tone signal; and said data signal communication section is abroadband communication section that performs modulation and transmitsand receives data by means of a broadband signal.
 25. The radiocommunication apparatus according to claim 24, further comprising are-synchronization control section that gives notification ofsynchronizing with a super-frame of another group that does not share asuper-frame to another radio communication apparatus belonging to thesame group as itself that shares a super-frame, monitors an end tone ofanother group in all super-frame periods, and when having received thatend tone, re-sets to a super-frame end and transmits an end tone viasaid narrowband communication section.
 26. The radio communicationapparatus according to claim 25, further comprising a beginning tonecontrol section that transmits a narrowband signal beginning tone 1 andbeginning tone 2 for collision avoidance in communication with aneighboring radio communication apparatus via said narrowbandcommunication section, or receives said beginning tone 1 and transmitssaid beginning tone 2 via said narrowband communication section, orreceives said beginning tone 1 and said beginning tone 2, and stopstransmission of beginning tone 1 in a current super-frame.
 27. The radiocommunication apparatus according to claim 26, further comprising: aprobe transmitting section that gives a directive for beginning tone 1transmission to said beginning tone control section, and upon subsequentnotification of reception of beginning tone 2 from that beginning tonecontrol section, gives a directive to said frame transmitting/receivingsection for transmission of a probe request frame requestingnotification of attribute and/or communication environment informationto another radio communication apparatus; and a probe receiving sectionthat, when having received said probe request, directs said frametransmitting/receiving section to transmit its own attribute andcommunication environment information.